Exhaust gas purifying apparatus, particulate filter and manufacturing method thereof

ABSTRACT

This invention relates to an exhaust gas purifying apparatus having a particulate filter for collecting particulates in exhaust gas. This particulate filter ( 22 ) contains partition walls defining paths ( 50, 51 ) in which exhaust gas flows. This partition wall is formed of porous material. This particulate filter ( 22 ) is created by gathering tips of the partition walls and then baking with the adjacent partition walls being in contact with each other. The adjacent partition walls are bonded together at a predetermined bonding strength if the partition walls are baked such that they are in contact. According to this invention, the end portion of the particulate filter ( 22 ) has a higher strength than the predetermined bonding strength.

FIELD OF THE INVENTION

[0001] The invention relates to an exhaust gas purifying apparatus,particulate filter and manufacturing method thereof.

BACKGROUND OF THE INVENTION

[0002] A particulate filter for collecting particulates in exhaust gasemitted from an internal combustion engine has been disclosed inpublished Japanese translation of PCT-application, JP-T-8-508199. Inthis particulate filter, a honeycomb structure is formed of porousmaterial and some of a plurality of paths (hereinafter referred to asfilter paths) in this honeycomb structure are closed at their upstreamends, while remaining filter paths are closed at their downstream ends.Consequently, exhaust gas flowing into the particulate filter alwayspasses through porous walls (hereinafter referred to as filter partitionwalls) forming the filter paths and flows out of the particulate filter.

[0003] In this particulate filter, since exhaust gas always passesthrough the filter partition wall and after that, flows out of theparticulate filter, its particulate collection rate is higher than theparticulate collection rate of a particulate filter in which exhaust gasonly passes through the filter paths without passing through thepartition walls of the particulate filter.

[0004] In the particulate filter disclosed in the above describedpublication, the filter path is closed by gathering the end portions ofthe filter partition walls and bonding together these end portions.Consequently, the exhaust gas flow-in opening in the filter path isshaped in a funnel. If the exhaust gas flow-in opening in the filterpath is shaped in a funnel, exhaust gas flows into the filter pathsmoothly without a turbulent flow. That is, no turbulent flow isgenerated in exhaust gas when exhaust gas flows into the filter path.Thus, pressure loss of the particulate filter disclosed in thepublication is low.

[0005] In the particulate filter of the above-described type, the filterpath is completely closed by gathering the end portions of the filterpartition walls such that the end portions are in contact with eachother and baking the end portions being in contact with each other so asto bond together the end portions. Consequently, the filter path iscompletely closed. However, when the end portions that are in contactwith each other are baked, these end portions are separated due to aninfluence of thermal expansion of the end portions and surroundingfilter partition walls, so that the filter path may not be completelyclosed.

DISCLOSURE OF THE INVENTION

[0006] It is an object of the invention to close the filter path at itsend portion securely in a particulate filter of the above-describedtype.

[0007] A first aspect of the invention relates to an exhaust gaspurifying apparatus having a particulate filter for collectingparticulates in exhaust gas. This particulate filter has a partitionwall, which defines a path in which exhaust gas flows. Then, thispartition wall is formed of porous material. This particulate filter iscreated by gathering tips of the partition walls such that adjacentpartition walls are brought into contact with each other and bakingthem. Due to the fact that the partition walls are baked in a statewhere they are in contact with each other, the adjacent partition wallsare bonded together at a predetermined bonding strength. Further,according to the first aspect of the invention, the end portion of theparticulate filter has a higher bonding strength than the predeterminedbonding strength.

[0008] The increased bonding strength can be achieved by a plurality ofmeasures. It is important that the predetermined bonding strength is tobe understood as the bonding strength which is achievable by the bakedcontact surface of end portions of adjacent wall plates bent towardseach other.

[0009] A second aspect of the invention relates to a manufacturingmethod of a particulate filter for collecting particulates in exhaustgas. This method includes the steps of forming a preliminary formed bodyhaving partition walls defining a path by extruding porous material,closing the path of the preliminary formed body by gathering an endportion of the partition wall of the preliminary formed body so thattips of adjacent end portions are in contact with each other, baking thepreliminary formed body, and reinforcing the closed portion in the path.

[0010] A third aspect of the invention relates to a manufacturing methodof the particulate filter for collecting particulates in exhaust gas.This method includes the steps of forming a preliminary formed bodyhaving partition walls defining a path by extruding porous material,closing the path of the preliminary formed body by gathering an endportion of the partition wall of the preliminary formed body so thattips of adjacent end portions are in contact with each other, baking thepreliminary formed body, and loading the end portion of the partitionwall closing the path of the preliminary formed body with a substancecapable of oxidizing particulates.

[0011] A fourth aspect of the invention relates to an exhaust gaspurifying apparatus having a particulate filter for collectingparticulates in exhaust gas. An end portion of a path of the particulatefilter includes a bonding portion bonded together at a predeterminedbonding strength when tips of adjacent partition walls formed of porousmaterial defining the path are brought in contact and are baked. In thefourth aspect of the invention, an average pore diameter of the bondingportion is smaller than an average pore diameter of other partition wallthan the end portion.

[0012] A fifth aspect of the invention relates to an exhaust gaspurifying apparatus having a particulate filter for collectingparticulates in exhaust gas. In the fifth aspect of the invention,adjacent partition walls are bonded together by baking over apredetermined length from the tip of the partition wall made of porousmaterial defining a path of the particulate filter such that theadjacent partition walls are in contact with each other and the adjacentpartition walls are boned in parallel with each other on a bondedportion of the partition walls.

[0013] A sixth aspect of the invention relates to a particulate filterfor collecting particulates in exhaust gas. This particulate filterincludes a body portion formed with partition walls made of porousmaterial defining a path in which the exhaust gas flows, and an endportion including a bonding portion bonded at a predetermined bondingstrength when tips of the adjacent partition walls are in contact witheach other and baked. In the sixth aspect of the invention, the endportion has a higher strength than the predetermined bonding strength.

[0014] A seventh aspect of the invention relates to a particulate filterfor collecting particulates in exhaust gas. This particulate filterincludes a body portion formed with partition walls made of porousmaterial defining a path in which the exhaust gas flows, and an endportion including a bonding portion bonded at a predetermined bondingstrength when tips of the adjacent partition walls are in contact witheach other and baked. In the seventh aspect of the invention., anaverage pore diameter of the bonding portion is smaller than an averagepore diameter of the partition wall of the body portion.

[0015] A eighth aspect of the invention relates to a particulate filterfor collecting particulates in exhaust gas. This particulate filterincludes a body portion formed with partition walls made of porousmaterial defining a path in which the exhaust gas flows, and a bondingportion baked with tips of the adjacent partition walls being in contactwith each other. In the eighth aspect of the invention, the bondingportion is formed by bonding such that the adjacent partition walls arein parallel with each other.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The foregoing and further objects, features and advantages of theinvention will become apparent from the following description ofpreferred embodiments with reference to the accompanying drawings,wherein like numerals are used to represent like elements and wherein:

[0017]FIGS. 1A, 1B are diagrams showing a particulate filter accordingto a first embodiment of the invention;

[0018]FIGS. 2A, 2B are diagrams showing an upstream end portion and adownstream end portion of the particulate filter of the firstembodiment;

[0019]FIGS. 3A, 3B are diagrams showing an upstream end portion and adownstream end portion of a conventional particulate filter;

[0020]FIG. 4A is a front view showing a honeycomb structure;

[0021]FIG. 4B is a side view showing the honeycomb structure,reinforcement member and die;

[0022]FIGS. 5A, 5B are diagrams showing the reinforcement member in FIG.4B;

[0023]FIGS. 6A, 6B are diagrams showing the die in FIG. 4B;

[0024]FIG. 7A is a diagram showing the particulate-filter of the secondembodiment;

[0025]FIG. 7B is a diagram showing the honeycomb structure and die ofthe second embodiment;

[0026]FIGS. 8A, 8B are diagrams for explaining oxidation process ofparticulates;

[0027]FIGS. 9A, 9C are diagrams for explaining deposition process ofparticulates; and

[0028]FIG. 10 is a diagram showing the relation between the amount ofoxidation removable particulates and the temperature of the particulatefilter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Hereinafter, the first embodiment of the invention will bedescribed with reference to the accompanying drawings. FIG. 1A is an endface diagram of the particulate filter and FIG. 1B is a longitudinalsectional view of the particulate filter. As shown in FIGS. 1A, 1B, theparticulate filter 22 has a honeycomb structure, containing a pluralityof exhaust gas paths extending in parallel. The exhaust gas pathconstituted by an exhaust gas flow-in path 50 whose downstream endopening is closed by a tapered wall (hereinafter referred to asdownstream tapered wall) 52 and an exhaust gas flow-out path 51 whoseupstream end opening is closed by a tapered wall (hereinafter referredto as upstream tapered wall) 53. Namely, some part of the exhaust gasflow path (exhaust gas flow path 50) is closed by the downstream taperedwall 52 at the downstream end thereof, while the remaining exhaust gasflow path (exhaust gas flow-out path 51) is closed by the upstreamtapered wall 53 at the upstream end thereof.

[0030] The downstream tapered wall 52 is formed by gathering andconnecting the downstream end partition portion of the partition wall,which defines the exhaust gas flow-in path 50 of the particulate filter22. On the other hand, the upstream tapered wall 53 is formed bygathering and connecting the upstream end partition portion of thepartition wall, which defines the exhaust gas flow-out path 51 of theparticulate filter 22.

[0031] According to the present embodiment, the exhaust gas flow-in path50 and the exhaust gas flow-out path 51 are arranged alternately througha thin partition wall 54. In other words, the exhaust gas flow-in paths50 and the exhaust gas flow-out paths 51 are constructed such that eachexhaust gas flow-in path 50 is surrounded by four exhaust gas flow-outpaths 51 while each exhaust gas flow-out path 51 is surrounded by fourexhaust gas flow-in paths 50. That is, one exhaust gas flow path(exhaust gas flow-in path 50) of two adjacent exhaust gas flow paths, isclosed completely by the downstream tapered wall 52 at the downstreamend thereof while the other exhaust gas flow path (exhaust gas flow-outpath 51) is closed completely by the upstream tapered wall 53 at theupstream end.

[0032] As shown in FIGS. 2A, 2B, reinforcement members 55, 56 areattached to tips of these tapered walls 52, 53. These reinforcementmembers 55, 56 are attached to the tapered walls 52, 53 so as to coverat least the tips of, or the entire tapered walls 52, 53.

[0033] The particulate filter 22 is formed of, for example, porousmaterial such as cordierite. Thus, exhaust gas flowing into the exhaustgas flow-in path 50 passes through the surrounding partition wall 54 asindicated by an arrow in FIG. 1B and flows into the adjacent exhaust gasflow-out path 51. Since the tapered walls 52, 53 are a part of thepartition wall 54, these tapered walls 52, 53 are, of course, alsoformed of the same porous material as the partition wall 54. Further,according to the present embodiment, since the reinforcement members 55,56 are also formed of porous material, exhaust gas passes through theupstream tapered wall 53 and the reinforcement member 56 as indicated byan arrow in FIG. 2A and flows into the exhaust gas flow-out path 51 andas indicated by an arrow in FIG. 2B, passes through the downstreamtapered wall 52 and the reinforcement member 55 and flows out.

[0034] The upstream tapered wall 53 is formed in a quadrangular pyramidshape in which the sectional area of the exhaust gas flow-out path 51 isgradually decreased as it approaches the upstream. Of course, thereinforcement member 56, which is attached so as to cover the upstreamtapered wall 53, is also formed in a quadrangular pyramid shape whichbecomes narrower as it approaches the upstream. Thus, the upstream endof the exhaust gas flow-in path 50, formed by four surrounding upstreamtapered walls 53 has a quadrangular pyramid shape in which the sectionalarea of the flow path is gradually increased toward the upstream. As aresult, as compared to a case where an intake opening of the exhaust gasflow-in path is formed as shown in FIG. 3A, exhaust gas flows into theparticulate filter more easily.

[0035] That is, in the particulate filter shown in FIG. 3A, the upstreamend of the exhaust gas flow-out path is closed by a plug 72. In thiscase, since part of exhaust gas collides with the plug 72 as indicatedwith a solid line, exhaust gas does not easily flow into the exhaust gasflow-in path. As a result, pressure loss of the particulate filter isincreased. Further, since exhaust gas flowing into the exhaust gasflow-in path from near the plug 72 becomes turbulent in the vicinity ofthe inlet as indicated with a dotted line, it is more difficult for theexhaust gas to flow into the exhaust gas flow-in path. As a result,pressure loss of the particulate filter is further increased.

[0036] On the other hand, the particulate filter 22 of the presentembodiment allows exhaust gas to flow into the exhaust gas flow-in path50 without causing any turbulent flow in exhaust gas as shown in FIG.2A. Thus, according to the present embodiment, exhaust gas can easilyflow into the particulate filter 22. Therefore, the pressure loss of theparticulate filter is small.

[0037] In the particulate filter shown in FIGS. 3A, 3B, particulates inexhaust gas are easily deposited on the upstream end face of the plug 72and the surface of the partition wall nearby. The reason for this isthat exhaust gas collides with the plug 72 and exhaust gas becomesturbulent near the plug 72. However, in the particulate filter 22 of thepresent embodiment, the upstream end face which exhaust gas stronglycollides with does not exist, since the upstream tapered wall 53.Further, the reinforcement member 56 are quadrangular pyramid andexhaust gas does not become turbulent near the upstream end face.Therefore, according to the present embodiment, a great number ofparticulates are not deposited on the upstream end region of theparticulate filter 22, so that the pressure loss of the particulatefilter 22 is suppressed.

[0038] On the other hand, the downstream tapered wall 52 of the presentembodiment is formed in a quadrangular pyramid shape such that thesectional area of the flow path of the exhaust gas flow-in path 50 isgradually decreased as it approaches the downstream. Of course, thereinforcement member 55 attached so as to cover the downstream taperedwall 52 is also formed to be accommodated in a quadrangular pyramidshape which becomes narrower as it approaches the downstream. Thus, thedownstream end of the exhaust gas flow-out path 51 formed by foursurrounding downstream tapered walls 52 expands in a quadrangularpyramid shape in which the sectional area is gradually decreased as itapproaches the downstream. As a result, exhaust gas easily flows out ofthe particulate filter as compared to a case where an exit opening ofthe exhaust gas flow-out path is formed as shown in FIG. 3B.

[0039] That is, in the particulate filter shown in FIG. 3B, thedownstream end of the exhaust gas flow-in path is closed by a plug 70and the exhaust gas flow-out path extends straight up to the exit. Inthis case, part of exhaust gas flowing out of the exit opening in theexhaust gas flow-out path flows along the downstream end face, so that aturbulent flow 71 is formed in the vicinity of the exit opening in theexhaust gas flow-out path. If a turbulent flow is formed in this way,exhaust gas does not easily flow out of the exhaust gas flow-out path.

[0040] On the other hand, in the particulate filter of the presentembodiment, as shown in FIG. 2B, no turbulent flow is formed in exhaustgas, so that the exhaust gas can flow out of the exit opening of theexhaust gas flow-out path 51. Thus, according to the present embodiment,exhaust gas relatively easily flows out of the particulate filter.Therefore, the pressure loss of the particulate filter 22 is small.

[0041] In the meantime, the tapered walls 52, 53 and the reinforcementmembers 55, 56 may be formed in any other form than the quadrangularpyramid, for example, conical as long as it becomes gradually narroweras it approaches outside of the particulate filter 22.

[0042] Next, the reinforcement member of the first embodiment will bedescribed in detail. The tapered walls 52, 53 of the particulate filter22 of the above-described type are formed by gathering the partitionwalls which define the paths in the honeycomb structure made of porousmaterial, that is, end portions of the partition walls 54 so that tipsthereof are in contact with each other and baking the honeycombstructure. That is, the end portions of the partition walls are baked,so that the end portions are bonded together.

[0043] Actually, when the honeycomb structure is baked, a hole may bemade in the tip of the tapered walls 52, 53 depending on a case, sincethe tips of the partition walls 54 are separated due to an influence ofthermal expansion of the end portions of the partition walls. Accordingto the present embodiment, since the basic configuration of theparticulate filter 22 is that the end portions of the exhaust gas flowpaths (exhaust gas flow-in path 50, exhaust gas flow-out path 51) areclosed completely by the tapered walls 52, 53, the hole is not made inthe tip of the tapered walls 52, 53 like this.

[0044] According to the present embodiment, before the honeycombstructure is baked, the reinforcement members 55, 56 are disposed at thetips of the tapered walls 52, 53 and after that, the honeycomb structureis baked. While the tapered walls 52, 53 are formed by bonding togetherthe tips of the separate partition walls 54, the reinforcement members55, 56 are integrated members. Therefore, they hold the tips of thepartition walls 54, which form the tapered walls 52, 53, so that they donot leave each other, when the honeycomb structure is baked.

[0045] According to the present embodiment, the bonding strength of thebonding region of the partition wall 54, which constructs the taperedwalls 52., 53, is increased, thereby preventing a hole from being madein the tips of the tapered walls 52, 53.

[0046] The average pore diameter of each of the reinforcement members55, 56 is determined by the degree of increase of the pressure loss ofthe entire particulate filter 22 when the reinforcement members 55, 56are attached to the tips of the tapered walls 52, 53 and the extent ofreinforcement necessary for preventing any hole from being made in thetips of the tapered walls 52, 53. That is, a reinforcement member havinga larger average pore diameter is used as the necessity of suppressingthe increase of the pressure loss is larger. Then, a reinforcementmember having a smaller average pore diameter is used as the level ofreinforcement needs to be increased. In the meantime, the average porediameter of the reinforcement member in the present embodiment issmaller than the average pore diameter of the partition wall 54.

[0047] As a modification of the first embodiment, the reinforcementmembers 55, 56, particularly the tips thereof may be loaded with asubstance capable of oxidizing particulates in exhaust gas.Consequently, the average pore diameter of the reinforcement members 55,56 becomes smaller than a case where they are loaded with no substancecapable of oxidizing particulates. Thus, even if a hole is made in thetip of the tapered walls 52, 53 when the honeycomb structure is baked,the average pore diameter of the tip of the reinforcement members 55, 56is small. Therefore, the particulates in exhaust gas are prevented fromflowing out of the particulate filter without being collected by theparticulate filter.

[0048] Of course, if the hole in the tip of the tapered walls 52, 53 isclosed by attaching the reinforcement members 55, 56 to the taperedwalls 52, 53 after the honeycomb structure is baked, at least the objectof the invention is achieved. In this case also, particulates in exhaustgas can be prevented from flowing out of the particulate filter 22securely without being collected by the reinforcement members 55, 56 byreducing the average pore diameter of the reinforcement members 55, 56,which are allowed to carry a substance capable of oxidizing theparticulates.

[0049] In the meantime, it is important to construct the particulatefilter 22 so that the pressure loss is latently small and keep thepressure loss from exceeding largely a latently achievable value duringuse of the particulate filter 22, in viewpoints of its performance.

[0050] That is, in case where an internal combustion engine is providedwith a particulate filter, operation control of the internal combustionengine is so designed considering the latent pressure loss of theparticulate filter. Even if the particulate filter is constructed so asto keep the pressure loss low, if the pressure loss exceeds its latentlyachievable value during use, the performance of the internal combustionengine is decreased.

[0051] Thus, according to the present embodiment, the partition wallwhich defines the upstream end region of the exhaust gas flow path inthe particulate filter 22 is formed of a tapered wall and further, thereinforcement member covering this partition wall is formed also of atapered member. Consequently, a turbulent flow is prevented when exhaustgas flows into the exhaust gas flow path so as to keep the pressure lossof the particulate filter 22 latently low.

[0052] As described above, the partition wall which defines the upstreamend region of the exhaust gas flow path in the particulate filter 22 isformed of the tapered wall and the reinforcement member covering thispartition wall is formed of the tapered member. Therefore, particulatesare not easily deposited on the wall of such tapered reinforcementmember. That is, the particulates are prevented from being deposited onthe wall of the tapered reinforcement member to produce a turbulent flowin exhaust gas flowing into the exhaust gas flow path during use of theparticulate filter 22. As a result, the pressure loss can be preventedfrom being increased far beyond its latently achievable value during useof the particulate filter 22.

[0053] As described above, particulates are not easily deposited on theupstream reinforcement member 56 during use of the particulate filter22. However, the particulates can be deposited on the upstreamreinforcement member 56. In this case, the pressure loss is increasedduring use of the particulate filter 22.

[0054] Thus, according to the above-described modification of theembodiment of the invention, the upstream reinforcement member 56 isloaded with a substance capable of oxidizing and removing particulatesso as to oxidize and remove the particulates deposited on the upstreamreinforcement member 56. As a result, since particulates collected bythe upstream reinforcement member 56 are continuously oxidized andremoved, no great number of the particulates are deposited on theupstream reinforcement member 56. Therefore, the pressure loss can bekept low during use of the particulate filter 22.

[0055] According to the present embodiment and its modification, aproblem inherent to the structure of closing the exhaust gas flow-outpath 51 that is, a problem that the pressure loss deviates from itsachievable value during use of the particulate filter can be avoided bythe upstream tapered wall 53 and the tapered reinforcement member 56made of porous material in order to reduce the pressure loss of theparticulate filter 22 latently.

[0056] According to the modification of the present embodiment, asubstance capable of oxidizing particulates is loaded on the entireparticulate filter 22, that is, not only on the upstream reinforcementmember 56, but also on the upstream tapered wall 53, the partition wall54, the downstream tapered wall 52 and the downstream reinforcementmember 55. Further, a substance capable of oxidizing particulates iscarried by not only the walls of the upstream reinforcement member 56,the upstream tapered wall 52, the partition wall 54, the downstreamtapered wall 52, and the downstream reinforcement member 55, but alsothese pore walls inside. According to the modification of the presentembodiment, the amount by a unit volume of the substance capable ofoxidizing particulates loaded on the upstream reinforcement member 56and the upstream tapered wall 53 is larger than the amount by a unitvolume of the substance capable of oxidizing particulates loaded on thepartition wall 54, the downstream tapered wall 52 and the downstreamreinforcement member 55.

[0057] According to the present embodiment, although the upstream endopening and the downstream end opening of the particulate filter areclosed completely, the concept of the invention can be applied to theparticulate filter in which only any one of the upstream end opening andthe downstream end opening is completely closed.

[0058] Next, a manufacturing method of a particulate filter of thepresent embodiment will be described briefly. First, a cylindricalhoneycomb structure 80 is formed of porous material such as cordieriteby extrusion as a preliminary formed body as shown in FIGS. 4A, 4B. Thehoneycomb structure 80 has a plurality of exhaust gas flow paths eachhaving a square section. Part of these exhaust gas flow paths serves asthe exhaust gas flow-in paths 50 in the particulate filter 22, while theremaining exhaust gas flow paths serves as the exhaust gas flow-outpaths 51 in the particulate filter 22.

[0059] Next, a reinforcement member 81 made of porous material isdisposed on each end face of the honeycomb structure 80 as shown in FIG.4B. As shown in FIG. 5A, each reinforcement member 81 has a disc portion82 fitting to a circular end face of the honeycomb structure 80. Asshown in FIG. 5A, a plurality of leg portions 83 extends vertically fromthe disc portion 82. As shown in FIG. 5B, each of these leg portions 82has a square of the square tube.

[0060] When the reinforcement member 81 is disposed on the end faceupstream of the honeycomb structure 80, each leg portion 83 isaccommodated in the exhaust gas flow-in path 50. On the other hand, whenthe reinforcement member 81 is disposed on the end face downstream ofthe honeycomb structure 80, each leg portion 83 is accommodated in theexhaust gas flow-out path 51. FIG. 5A indicates a sectional view takenalong the lines 5A-5A in FIG. 5B.

[0061] Next, a die 90 shown in FIG. 6 is pressed to the end face of thehoneycomb structure 80 together with the reinforcement member 81. Thedie 90 is pressed to one end face of the honeycomb structure 80 and thento the other end face. Of course, it is permissible to prepare two dies90 and press them to each end face of the honeycomb structure 80 at thesame time.

[0062] As shown in FIG. 6A, the die 90 has a plurality of quadrangularpyramid shaped protrusions 91. FIG. 6B shows a protrusion 91. The die 90is pressed to an end face of the honeycomb structure 80 together withthe reinforcement member 81 such that the protrusions 91 are insertedinto each predetermined exhaust gas flow path. When the protrusions 91of the die 90 are inserted into predetermined exhaust gas flow paths,the disc portion 82 of the reinforcement member 81 is broken by theseprotrusions 91. If the die 90 is moved further toward the end face ofthe honeycomb structure 80, the disc portion 82 and the leg portion 83of the reinforcement member 81 are gathered. At the same time, thepartition walls 54, which form a predetermined exhaust gas flow path,are gathered so as to form the tapered walls 52, 53. Consequently, thepredetermined exhaust gas flow paths are closed completely by thetapered walls 52, 53 covered by the reinforcement members 55, 56.

[0063] Next, the honeycomb structure 80 is dried, and then, thehoneycomb structure 80 is baked. Next, the honeycomb structure is loadedwith a substance capable of oxidizing particulates. As a result, theparticulate filter 22 is formed.

[0064] As described above, the end portion of the particulate filter 22is closed by the tapered walls 52, 53 composed of the same porousmaterial as the partition wall 54. Therefore, the exhaust gas flow path(exhaust gas flow-in path 50, exhaust gas flow-out path 51) of theparticulate filter 22 can be closed by the same material as thepartition wall 54 according to such a simple method of pressing the die90 against the end face of the honeycomb structure 80 as describedabove.

[0065] The step of disposing the reinforcement member 81 on the end faceof the honeycomb structure 80 and pressing the die 90 against the endface of the honeycomb structure 80 may be executed after the honeycombstructure 80 is dried. Alternatively, it is permissible to soften theend portion of the honeycomb structure 80 after the honeycomb structure80 is baked, then dispose the reinforcement member 81 on the end face ofthe honeycomb structure 80 and press the die 90 to the softened endportion. In this case, the end portion of the honeycomb structure 80 isbaked again after that.

[0066] As a second modification of the present embodiment, aquadrangular pyramid shaped reinforcement member composed of porousmaterial may be disposed directly on the tapered wall after thehoneycomb structure 80 is baked.

[0067] Although the leg portion 83 of the reinforcement member 81 ismeans for positioning securely and holding the reinforcement member 81on the honeycomb structure, the leg portion 83 may be eliminated ifother means for achieving this is provided.

[0068] Next, the particulate filter of the second embodiment will bedescribed. According to the second embodiment, as shown in FIG. 7A, theend portions of the partition walls 54 are bonded over a predeterminedlength from the tip so as to form extended portions 57, 58. In thedownstream region of the particulate filter 22, the end portionsdownstream of the partition walls 54 are bonded together with adjacentparallel portions over a predetermined length toward the upstream fromthe tip so as to form an extended portion 57. On the other hand, in theupstream region of the particulate filter 22, the end portions upstreamof the partition walls 54 are bonded together over a predeterminedlength toward downstream from the tip so as to form an extended portion58.

[0069] As shown in FIG. 7B, these extended portions 57, 58 are formed bypressing the die 90 having the quadrangular pyramid shaped protrusions91 and a rectangular portion 92 adjacent to this protrusion 91 andfurther containing a groove 93 between these rectangular portions 92against each end face of the honeycomb structure 80.

[0070] Thus, according to the present embodiment, the bonding region ofthe end portions bonded together of the partition walls 54 in the endportion region of the particulate filter 22 is larger than the bondingregion when only the tips of the partition walls are bonded together.For this reason, the bonding strength of the partition walls in the endportion region of the particulate filter 22 of the present embodiment ishigher than the bonding strength when only the tips of the partitionwalls are bonded together.

[0071] As a modification of the second embodiment, the bonding strengthof the end portions of the partition walls 54 which construct theextended portions 57 can be increased by loading on the extendedportions 57, 58 with a substance capable of oxidizing the particulates.Of course, the entire particulate filter 22 may be loaded with theaforementioned substance capable of oxidizing the particulates.

[0072] In case of loading the honeycomb structure 80 with a substancecapable of oxidizing particulates according to the present embodiment,the step of loading the honeycomb structure 80 with this substancecapable of oxidizing particulate is carried out after the step of bakingthe honeycomb structure 80.

[0073] Next, the particulate filter 22 of the third embodiment will bedescribed. The structure and operation of the particulate filter 22 ofthe third embodiment are the same as those of the first embodimentexcept the items described below. Therefore, description about the samestructure and operation as the first embodiment is omitted.

[0074] According to the third embodiment, the reinforcement members 55,56 of the first embodiment are omitted. According to the thirdembodiment, in place of them, the average pore diameter of the endportions of the partition walls 54 to be bonded together so as to formthe tapered walls 52, 53 is set smaller than the average pore diameterof the partition wall 54.

[0075] According to the present embodiment, assuming a case where theareas of the end portions of the partition walls 54 bonded together areequal, the area of the end portions of the partition walls 54substantially being in contact with each other is larger than a bondingregion of tips in an end portions having the same average pore diameteras the partition wall 54. Therefore, the bonding strength of thepartition walls in an end portion region of the particulate filter 22 ofthe present embodiment is higher than the bonding strength of a casewhere the end portions having the same pore density as the partitionwall 54 are bonded to each other.

[0076] According to the present embodiment also, it is of coursepermissible to increase the bonding strength of the tips of thepartition walls 54 by loading the end portions of the partition walls 54bonded together with a substance capable of oxidizing the particulates.

[0077] According to the present embodiment, a step of reducing theaverage pore diameter of the end portions of the partition walls 54 tobe bonded together may be executed between a step of closing the exhaustgas flow path in the honeycomb structure 80 with the end portions and astep of baking the honeycomb structure 80. A step of loading thehoneycomb structure 80 with a substance capable of oxidizing theparticulates may be carried out after a step of baking the honeycombstructure 80.

[0078] Next, a particulate filter of the fourth embodiment will bedescribed. According to the present embodiment, the bonding strength ofthe tips of the end portions of the partition walls to be bondededtogether is incresed in order to prevent the tips of the end portions ofthe partition walls, which compose the tapered wall, from beingseparated and producing a hole when the honeycomb structure is baked.That is, an object of the above-described embodiment is to prevent ahole from being made in the tip of the tapered wall.

[0079] The object of the fourth embodiment is to prevent exhaust gasfrom flowing out of a hole in the tip of the tapered wall by closing thehole made in the tip of the tapered wall in a simple way. Morespecifically, according to the fourth embodiment, a hole made in the tipof each of the tapered walls 52, 53 is closed by loading the tips of thetapered walls 52, 53 with a substance capable of oxidizing theparticulates after the honeycomb structure 80 is baked.

[0080] Finally, a substance capable of oxidizing particulates loaded onthe particulate filter 22 will be described in detail. According to theabove-described embodiment, a carrier layer made of alumina and the likeis formed on the peripheral wall face of each exhaust gas flow-in path50 and the inside of the peripheral walls and each exhaust gas flow-outpath 51 i.e., both side surfaces and inside of each partition wall 54,both side surface and inside of the tapered walls 52, 53, and both sidesurfaces and inside of a reinforcement member if it is provided. Then,this carrier is loaded with noble metal catalyst and active oxygendischarging agent which if excessive oxygen exists, takes in and retainsoxygen and if the concentration of oxygen decreases, releases theretained oxygen in the form of active oxygen. According to theabove-described embodiments, this the substance capable of oxidizing theparticulates is the active oxygen discharging agent.

[0081] According to the above-described embodiments, platinum Pt is usedas noble metal catalyst and as active oxygen discharging agent, at leastone selected from alkaline metals such as potassium K, sodium Na,lithium Li, cesium Cs, rubidium Rb, alkaline earth metals such as bariumBa, calcium Ca, strontium Sr, rare earth elements such as lanthanum La,yttrium Y, cerium Ce, transition metal such as iron Fe, and carbon groupelement such as tin Sn is employed.

[0082] It is preferable to use alkaline metal or alkaline earth metalensuring a higher ionization tendency than calcium Ca, such as potassiumK, lithium Li, cesium Cs, rubidium Rb, barium Ba, and strontium Sr.

[0083] Next, an action for removing particulates from exhaust gas bymeans of the particulate filter 22 will be described about a case whereplatinum Pt and potassium K are loaded on a carrier. The sameparticulate removal action is carried out if other noble metals,alkaline metals, alkaline earth metals, rare earth elements, ortransition metals are employed.

[0084] For example, if exhaust gas flowing into the particulate filter22 is gas emitted from a compression ignition type internal combustionengine which burns with excessive air, exhaust gas flowing into theparticulate filter 22 contains a great amount of excessive air. That is,if the ratio between air and fuel supplied into an intake air path and afuel combustion chamber is referred to as air-fuel ratio of exhaust gas,the air-fuel ratio of exhaust gas in the compression ignition typeinternal combustion engine is lean. Further, since NO is generated inthe fuel combustion chamber of the compression ignition type internalcombustion engine, NO is contained in exhaust gas. Added to that, sulfurcomponent S is contained in fuel and this sulfur component S reacts withoxygen in the fuel combustion chamber so as to produce SO₂. Therefore,SO₂ is contained in exhaust gas. Thus, exhaust gas containing excessiveoxygen, NO, and SO₂ flows into the exhaust gas flow-in path 50 of theparticulate filter 22.

[0085]FIGS. 8A, 8B show schematically an enlarged diagram of the surfaceof a carrier formed on an inner peripheral face of the exhaust gasflow-in path 50. In FIGS. 8A, 8B, the particulate 60 is a particulate ofplatinum Pt and the active oxygen discharging agent 61 containspotassium K.

[0086] As described above, since exhaust gas contains a large amount ofexcessive oxygen, if exhaust gas flows into the exhaust gas flow-in path50 in the particulate filter 22, oxygen O₂ adheres to the surface ofplatinum Pt 60 in the form of O₂ or O²⁻. On the other hand, NO inexhaust gas reacts with O₂ ⁻ or O²⁻ on the surface of platinum Pt 60 soas to produce NO₂ (2NO+O₂→2NO₂) Part of NO₂ generated next is oxidizedon platinum Pt 60 and absorbed into the active oxygen discharging agent61 and then combined with potassium K so that it is diffused into theactive oxygen discharging agent 61 in the form of nitrate ion NO₃ ⁻ andproduces potassium nitrate KNO₃.

[0087] On the other hand, SO₂ is contained in exhaust gas as describedabove and this SO₂ is absorbed in the active oxygen discharging agent 61in the same mechanism as NO. That is, as described above, oxygen O₂adheres to the surface of platinum Pt 60 in the form of O₂ ⁻ or O²⁻ andSO₂ in exhaust gas reacts with O₂ ⁻ or O²⁻ on the surface of platinum Pt60 and turns to SO₃. Part of SO₃ generated next is oxidized on platinumPt 60 and absorbed into the active oxygen discharging agent 61, so thatit is combined with potassium K and diffused into the active oxygendischarging agent 61 in the form of sulfuric ion SO₄ ²⁻ so as to producepotassium sulfate K₂SO₄. As a result, potassium nitrate KNO₃ andpotassium sulfate K₂SO₄ are generated.

[0088] On the other hand, particulates composed of mainly carbon C aregenerated in a combustion chamber and therefore, these particulates arecontained in exhaust gas. When exhaust gas flows in the exhaust gasflow-in path 50 in the particulate filter 22 or flows from the exhaustgas flow-in path 50 to the exhaust gas flow-out path 51, theseparticulates 62 contained in exhaust gas come into contact with andadhere to the surface of a carrier, for example, the active oxygendischarging agent 61.

[0089] If particulates 62 adhere to the surface of the active oxygendischarging agent 61, the concentration of oxygen on the contact facebetween the particulates 62 and the active oxygen discharging agent 61decreases. If the concentration of oxygen decreases, a difference in theconcentration of oxygen occurs between the contact face of the activeoxygen discharging agent 61 and the active oxygen discharging agent 61whose concentration of oxygen is higher, so that oxygen in the activeoxygen discharging agent 61 tries to move toward the contact facebetween the particulates 62 and the active oxygen discharging agent 61.As a result, potassium nitrate KNO₃ formed in the active oxygendischarging agent 61 is decomposed to potassium K, oxygen O and NO.Oxygen 0 moves toward the contact face between the particulates 62 andthe active oxygen discharging agent 61, while NO is discharged out ofthe active oxygen discharging agent 61. NO discharged out is oxidized onplatinum Pt 60 downstream and absorbed into the active oxygendischarging agent 61 again.

[0090] In addition, potassium sulfate K₂SO₄ formed in the active oxygendischarging agent 61 is decomposed to potassium K, oxygen O, and SO₂.Oxygen 0 moves toward the contact face between the particulates 62 andthe active oxygen discharging agent 61, while SO₂ is discharged out ofthe active oxygen discharging agent 61. SO₂ discharged out is oxidizedon platinum Pt 60 downstream and absorbed into the active oxygendischarging agent 61 again. However, since potassium sulfate K₂SO₄ isstable and difficult to decompose, potassium sulfate K₂SO₄ does noteasily emit active oxygen than potassium nitrate KNO₃.

[0091] The active oxygen discharging agent 61 generates and dischargesactive oxygen also in a reaction process with oxygen when NO_(x) isabsorbed in the form of nitrate ion NO₃ ⁻ as described above. Likewise,the active oxygen discharging agent 61 generates and discharges activeoxygen in a reaction process with oxygen when SO₂ is absorbed in theform of sulfate ion SO₄ ²⁻.

[0092] Oxygen O that moves toward the contact face between theparticulates 62 and the active oxygen discharging agent 61 is oxygenwhich is generated by decomposing such compound as potassium nitrateKNO₃; potassium sulfate K₂SO₄. Oxygen O generated by decomposing thecompound has a high energy and an extremely high activity. Thus, oxygenwhich moves toward the contact face between the particulates 62 and theactive oxygen discharging agent 61 acts as active oxygen O. Likewise,oxygen generated in a reaction process between NO_(x) and oxygen in theactive oxygen discharging agent 61 or in a reaction process between SO₂and oxygen acts as active oxygen. If the active oxygen O are in contactwith the particulates 62, the particulates 62 are oxidized without anyluminous flame in a short time (several seconds to several tensminutes), so that the particulates 62 are vanished completely.Therefore, the particulates 62 are hardly deposited on the particulatefilter 22.

[0093] Some type of the particulate filter is heated in red and burnsthe particulates with flame when particulates deposited in layers on theparticulate filter are burned. The combustion with a flame does notcontinue unless a high temperature is kept. Therefore, the temperatureof the particulate filter has to be kept high in order to continuecombustion with the flame.

[0094] According to the embodiment of the invention, the particulates 62are oxidized without any luminous flame as described above, and thesurface of the particulate filter 22 is not heated in red. In otherwords, according to the embodiment of the invention, the particulates 62are oxidized and removed under a relatively lower temperatures ascompared to combustion with flame. Therefore, the particulate removalaction by oxidation of particulates 62 without any luminous flameaccording to the embodiment of the invention is completely differentfrom the particulate removal action by combustion with flame.

[0095] Since platinum Pt 60 and active oxygen discharging agent 61 areactivated more as the temperature of the particulate filter 22 isincreased, the amount of oxidation removable particulates withoutluminous flame per unit time on the particulate filter 22 is increasedas the temperature of the particulate filter 22 is increased.

[0096] A solid line in FIG. 10 indicates the amount G of oxidationremovable particulates without luminous flame per unit time. Thehorizontal axis in FIG. 10 indicates the temperature TF of theparticulate filter 22. Hereafter, the amount of particulates flowinginto the particulate filter 22 per unit time is referred to as flow-inparticulate amount M. If this flow-in particulate amount M is smallerthan the oxidation removable particulates G i.e., within a region I inFIG. 10, all particulates flowing into the particulate filter 22 beingcontact with the particulate filter 22 are oxidized without any luminousflame on the particulate filter 22 in a short time (several seconds toseveral ten minutes) and removed.

[0097] Contrary to this, if the flow-in particulate amount M is largerthan the oxidation removable particulate amount G i.e., within a regionH in FIG. 10, the amount of active oxygen is not enough for oxidizingall particulates. FIGS. 9A to 9C show the state of oxidation ofparticulates in such a case. That is, if the amount of active oxygen isshort for oxidizing all particulates and the particulates 62 adhere tothe active oxygen discharging agent 61 as shown in FIG. 9A, only part ofthe particulates 62 is oxidized, while part of the particulates which isnot oxidized sufficiently remains on the carrier. If the state in whichthe active oxygen amount is not enough continues, particulates which arenot sufficiently oxidized remain on the carrier successively, so that asshown in FIG. 9B, the surface of the carrier is covered with remainingparticulate portion 63.

[0098] If the surface of the carrier is covered with the remainingparticulate portion 63, oxidation of NO and SO₂ by platinum Pt 60 anddischarge of active oxygen by the active oxygen discharging agent 61 areeliminated, so that the remaining particulate portion 63 is left withoutbeing oxidized and slightly after, other particulates are depositedsuccessively on the remaining particulate portion 63 as shown in FIG.9C. That is, the particulates are deposited in layers.

[0099] If the particulates are deposited in layers, the particulates 64are never oxidized by active oxygen 0 and therefore, other particulatesare deposited successively on the particulates 64. That is, if the statein which the flow-in particulate amount M is larger than the oxidationremovable particulate amount G is continued, particulates are depositedin layers on the particulate filter 22 and the deposited particulatescannot be ignited and burnt until the temperature of exhaust gas israised high or the temperature of the particulate filter 22 is raisedhigh.

[0100] In the region I of FIG. 10, particulates are oxidized on theparticulate filter 22 without any luminous flame in a short time and inthe region II of FIG. 10, particulates are deposited in layers on theparticulate filter 22. Thus, the flow-in particulate amount M alwaysneeds to be smaller than the oxidation remove particulate amount G forthe particulates not to be deposited in layers on the particulate filter22.

[0101] As evident from FIG. 10, the particulate filter 22 used in theembodiments of the invention is capable of oxidizing particulates evenif the temperature TF of the particulate filter 22 is quite low. Thus,the flow-in particulate amount M and the temperature TF of theparticulate filter 22 are kept so that the flow-in particulate amount Mis always smaller than the oxidation removable particulate amount G.

[0102] If the flow-in particulate amount M is always smaller than theoxidation removable particulate amount G, few particulates are depositedon the particulate filter 22, so that the back pressure is increasedlittle.

[0103] On the other hand, if particulates are deposited in layers on theparticulate filter 22 as described above, even if the flow-inparticulate amount M becomes smaller than the oxidation removableparticulate amount G, it is difficult to oxidize the particulates withactive oxygen 0. That is, if the flow-in particulate amount M becomessmaller than the oxidation removable particulate amount G when theparticulates are deposited only below a predetermined level, thisremaining particulate portion is oxidized without any luminous flame bythe active oxygen O and removed.

[0104] If a case in which the particulate filter 22 is disposed in theexhaust gas path of an internal combustion engine and actually employedis considered, fuel and lubricant contain calcium Ca and therefore,calcium Ca is contained in exhaust gas. If SO₃ exists, this calcium Cagenerates calcium sulfate CaSO₄. This calcium sulfate CaSO₄ is solid,which is not thermally decomposed even at a high temperature. Thus, ifcalcium sulfate CaSO₄ is generated and the pore in the particulatefilter 22 is closed by this calcium sulfate CaSO₄, exhaust gas does noteasily flow in the particulate filter 22.

[0105] In this case, if alkaline metal or alkaline earth metal having ahigher ionization tendency than calcium Ca, for example, potassium K isemployed as the active oxygen discharging agent 61, SO₃ diffused in theactive oxygen discharging agent 61 is combined with potassium K so as toform potassium sulfate K₂SO₄. Calcium Ca passes through the partitionwall 54 of the particulate filter 22 without being combined with SO₃ andflows out into the exhaust gas flow-out path 51. Thus, the pores in theparticulate filter 22 are never clogged. Therefore, preferably, as theactive oxygen discharging agent 61, alkaline metal or alkaline earthmetal having a higher ionization tendency than calcium Ca i.e.,potassium K, lithium Li, cesium Cs, rubidium Rb, barium Ba, or strontiumSr is employed.

[0106] The embodiments of the invention can be applied to a case whereonly noble metal such as platinum Pt 60 is loaded on the layer of acarrier formed on both side faces of the particulate filter 22. However,in this case, the solid line indicating the oxidation removableparticulate amount G is moved slightly to the right as compared to thesolid line shown in FIG. 10. In this case, active oxygen is dischargedfrom NO₂ or SO₃ retained on the surface of the platinum Pt 60.

[0107] Further, it is permissible to employ a catalyst, which absorbsNO₂ or SO₃ as the active oxygen discharging agent and can dischargeactive oxygen from these absorbed NO₂ or SO₃.

1. A particulate filter having: a partition wall made of porous materialfor defining a path allowing exhaust gas to flow; and an end portion inwhich an opening of the path is closed by a bonding portion bondedtogether at a predetermined bonding strength when tips of the partitionwalls gathered so that they contact each other are baked, for collectingparticulates in exhaust gas, characterized by comprising a reinforcementmember that reinforces the bonding portion provided at the end portionby covering the tapered walls of the partition walls at their endportions.
 2. An exhaust gas purifying apparatus comprising theparticulate filter according to claim
 1. 3. The exhaust gas purifyingapparatus according to claim 2, wherein the reinforcement member is amember made of porous material, loaded with a substance capable ofoxidizing the particulates.
 4. The exhaust gas purifying apparatusaccording to claim 2, wherein an average pore diameter of thereinforcement member is smaller than an average pore diameter of thepartition wall.
 5. The exhaust gas purifying apparatus according toanyone of claims 2 to 4, wherein the adjacent partition walls at the endportion are bonded together over a predetermined length from the tip ofthe partition wall.
 6. The exhaust gas purifying apparatus according toclaim 5, wherein the adjacent partition walls to be bonded together areparallel over the predetermined length from the tip of the partitionwall.
 7. The exhaust gas purifying apparatus according to anyone ofclaims 2 to 6, wherein the tips of the adjacent partition walls arebonded together through a predetermined contact area wherein a contactarea of the tips of the adjacent partition walls is increased byincreasing the contact area per unit area of the tips at the bondingportion.
 8. The exhaust gas purifying apparatus according to claim 7,wherein by decreasing an average pore diameter of the bonding portion,the contact area is increased.
 9. The exhaust gas purifying apparatusaccording to claim 8, wherein by loading the bonding portion with asubstance capable of oxidizing the particulates, the average porediameter of the bonding portion is decreased.
 10. The exhaust gaspurifying apparatus according to claim 9, wherein the partition wall isloaded with a substance capable of oxidizing the particulates and theamount of substance loaded on the bonding portion is larger than theamount of the substance loaded on a portion of the partition wall otherthan the bonding portion.
 11. The exhaust gas purifying apparatusaccording to anyone of claims 2 to 6, wherein the bonding portion isloaded with a substance capable of oxidizing the particulates.
 12. Theexhaust gas purifying apparatus according to anyone of claims 2 to 11,wherein the particulate filter contains a plurality of paths and in partof the paths, downstream end portions of the partition walls definingthe paths are gathered while in the remaining paths, upstream endportions defining the paths are gathered.
 13. A manufacturing method ofa particulate filter for collecting particulates in exhaust gas,comprising: forming a preliminary formed body having partition wallsdefining a path by extruding porous material; closing the path of thepreliminary formed body by gathering an end portion of the partitionwall of the preliminary formed body so that tips of adjacent endportions are in contact with each other; baking the preliminary formedbody; and reinforcing the closed portion in the path by covering thetapered walls of the partition walls at their end portions.
 14. Themanufacturing method according to claim 13, wherein the closed portionis reinforced by disposing a reinforcement member at the end portion ofthe partition walls of the preliminary formed body, gathering the tipsof the partition walls of the preliminary formed body together with thereinforcement member, closing the path of the preliminary formed body bybringing the tips of the end portions into contact with each other andbaking the preliminary formed body and the reinforcement member.
 15. Themanufacturing method according to claim 13, wherein after the path ofthe preliminary formed body is closed, the closed portion is reinforcedby providing the end portion with the reinforcement member.
 16. Themanufacturing method according to anyone of claims 13 to 15, wherein theclosed portion is reinforced by loading the tip of the partition wallwith a substance capable of oxidizing particulates.
 17. A manufacturingmethod of the particulate filter for collecting particulates in exhaustgas comprising: forming a preliminary formed body having partition wallsdefining a path by extruding porous material; closing the path of thepreliminary formed body by gathering an end portion of the partitionwall of the preliminary formed body so that tips of adjacent endportions are in contact with each other; baking the preliminary formedbody; and loading the end portion of the partition wall closing the pathof the preliminary formed body with a substance capable of oxidizingparticulates.
 18. The manufacturing method according to anyone of claims13 to 17, further comprising a step of: reducing an average porediameter of the end portion of the partition wall closing the path inthe preliminary formed body between closing the path and baking thepreliminary formed body.
 19. A particulate filter for collectingparticulates in exhaust gas having: a body portion formed with partitionwalls made of porous material defining a path in which the exhaust gasflows; and an end portion including a bonding portion bonded at apredetermined bonding strength when tips of the adjacent partition wallsare in contact with each other and baked, characterized in that anamount of substance capable of oxidizing the particulates loaded on theend portion is larger than the amount of the substance loaded on aportion of the partition wall other than: the: end portion.
 20. Theparticulate filter according to claim 19, wherein the substance capableof oxidizing the particulates is loaded on the bonding portion only. 21.An exhaust gas purifying apparatus comprising: the particulate filteraccording to claim 19 or
 20. 22. An exhaust gas purifying apparatuscomprising: a particulate filter for collecting particulates in exhaustgas and a reinforcement member provided at an end portion of a path ofthe particulate filter, wherein the end portion of the path of theparticulate filter includes a bonding portion bonded together at apredetermined bonding strength when tips of adjacent partition wallsformed of porous material defining the path are brought into contact andbaked, and wherein said reinforcement member covers the tapered walls ofthe partition walls at their end portions.
 23. A particulate filter forcollecting particulates in exhaust gas comprising: a particulate filterfor collecting particulates in exhaust gas wherein an end portion of apath of the particulate filter including the bonding portion bonded at apredetermined bonding strength when tips of the adjacent partition wallsare in contact with each other and baked, and an amount of substancecapable of oxidizing the particulates loaded on the bonding portion islarger than the amount of the substance loaded on a portion of thepartition wall other than the end portion.
 24. The particulate filteraccording to claim 23, wherein the substance capable of oxidizing theparticulates is loaded on the bonding portion only.
 25. A particulatefilter for collecting particulates in exhaust gas comprising: a bodyportion formed with partition walls made of porous material defining apath in which the exhaust gas flows; an end portion including a bondingportion bonded at a predetermined bonding strength when tips of theadjacent partition walls are in contact with each other and baked; and areinforcement member that reinforces the bonding portion provided at theend portion by covering the tapered walls of the partition walls attheir end portions.
 26. A particulate filter for collecting particulatesin exhaust gas comprising: a body portion formed with partition wallsmade of porous material defining a path in which the exhaust gas flows;and a bonding portion baked with tips of the adjacent partition wallsbeing in contact with each other, wherein an amount of substance capableof oxidizing the particulates loaded on the bonding portion is largerthan the amount of the substance loaded on a portion of the partitionwall other than the end portion.
 27. The particulate filter according toclaim 26, wherein the substance capable of oxidizing the particulates isloaded on the bonding portion only.